Palm-Size Satellites Could Hunt for Alien Worlds

Tiny satellites could hitch a ride into orbit and spot alien worlds from afar, new research suggests.

NASA's 2,230-pound (1,052 kilogram) Kepler Space Telescope has discovered thousands of potential planets around other stars. Now, some scientists want to go smaller: They propose searching for new worlds using miniaturized satellites that can fit in the palm of your hand.

"We want to be cheaper than sending up a huge satellite, to be able to collect more data in less time for less money," Ameer Blake, an undergraduate student at Howard University in Washington, D.C., told Space.com. Blake and his adviser, Aki Roberge, a research astrophysicist at NASA Goddard Space Flight Center, studied the possibility of using a smaller instrument known as a cubesat to search for a new planet around the star Beta Pictoris, already known to host at least one world, Beta Pictoris b. He presented the results in January at the American Astronomical Society meeting in Kissimmee, Florida. [CubeSats: Tiny, Versatile Spacecraft Explained (Infographic)]

"We wanted to know, are there any other planets other than Beta Pictoris b, and if so, where are they?" Blake said.

Small but powerful

In 2008, scientists used NASA's Hubble Space Telescope to reveal a giant planet more than 1.5 times the radius of Jupiter orbiting Beta Pictoris. Circling only nine times the Earth-sun distance from its star, just inside what would be the orbit of Saturn in the solar system, Beta Pictoris b is the closest orbiting exoplanet captured by direct imaging, the technique that essentially photographs other worlds. The method is most sensitive to giant planets several times the mass of Jupiter, and faces challenges when it comes to spotting smaller worlds or worlds close to their star.

Blake and Roberge are interested in launching a cubesat into space to search for a new world around the star. The evidence suggests the star's system sits nearly edge-on as seen from Earth - that is, oriented so we're looking at the edge of the system rather than from above or below. Researchers have seen a debris disk that stretches to over 1,400 times the Earth-sun distance on both sides of the star, and the known planet's orbit also agrees with that orientation. This should allow a cubesat to search for other planets using a process called the transit method, which should be able to see worlds inside the orbit of Beta Pictoris b.

Unlike direct imaging, which relies on capturing the light reflected from a planet, the transit method, which is also used by the Kepler telescope, searches for dips in the brightness of the star as a planet moves between it and Earth. Instruments can only detect the transiting planets' presence if they pass between the star and Earth, so the system must lie within a few degrees of being edge-on to Earth.

Stare & collect

Several years ago, planet hunter Sara Seager, of the Massachusetts Institute of Technology, proposed using a fleet of cubesats to survey part of the sky in search of worlds beyond the solar system. Blake said the idea inspired him and his adviser to consider a single instrument targeting only one star. This avoids concerns about focusing or redirecting a suite of satellites.

"This is just, stare at one thing and collect as much information as possible," Blake said.

Blake said that sending up a single satellite would make a good first step toward an entire fleet. Once the method is proven to work, other satellites could be launched to either discover new worlds or confirm preliminary observations, such as those made by Kepler.

When it comes to discovery, however, the search would need to be limited to stars which already demonstrate that their systems are edge-on to Earth. Researchers can identify such stars by observing massive debris disks around them or targeting stars with directly imaged worlds whose orbits are edge-on.

Cubesats were first introduced in 1999 as compact satellites that university students could construct to perform experiments and test new technologies. They take the standardized shape of a 4 x 4 x 4-inch (10 x 10 x 10 centimeters) cube, which allows them to hitch a ride into space with other, larger launches. Two will be launched in March 2016 to cover the entry, descent, and landing of NASA's upcoming Mars InSight lander, while other scientists have discussed dropping them off at destinations such as Europa and Enceladus. [CubeSats Are Bound For The Planets (Video)]

The biggest challenge for a cubesat mission to hunt for worlds around a specific target has to do with time. The scientific community requires at least three transits - three times an object must pass between its sun and the Earth - to confirm its status as a planet. Blake's study suggests a maximum of a year and a half for a cubesat orbit, though it may last for only half a year. To confirm a planet would require finding those which circle their stars every two to six months.

Blake and Roberge have performed the background study that shows using a cubesat to search for worlds around Beta Pictoris is a viable plan. Their next step is to speak to engineers and instrumentalists to determine what parts would be necessary to construct such a satellite. From there, they can make estimates on what building it might cost - though it should come in far less than Kepler's $550 million price tag.

"I think it would be great to be able to find exoplanets with less material and preferably in quicker time," Blake said.

The world's newest satellite launch site is off to a busy start, with 16 spacecraft put into orbit within a week -- and no rocket required.
What’s the trick? Well, the launch site itself is in space. The satellites -- tiny Earth-imagers owned by Silicon Valley startup Planet Labs -- were deployed into orbit over the past week from aboard the International Space Station.

Planet Labs is the first customer to make use of a new small satellite launcher owned by NanoRacks, another commercial space firm. NanoRacks' so-called "cubesat deployer" (photographed here in action) was flown to the station last month and installed in Japan’s Kibo laboratory. The module includes an exposed back porch, accessible via a small airlock and robotic arm. Japan also operates its own cubesat launcher on Kibo.

Like the station, the Planet Labs constellation, known as Flock 1, will fly in orbits inclined about 52 degrees above and below the equator. They will be lower than the station’s 250-mile altitude to prevent any potential collisions.